Master Electrician Calculations: The Subjects Your State’s Exam Tests

Not every state runs its master electrician exam the same way. Texas splits the examination into two separately scored portions delivered by PSI on behalf of the Texas Department of Licensing and Regulation (TDLR): NEC Knowledge and Calculations. The Calculations portion is 33 items — 30 scored and 3 non-scored pretest items — and you get 170 minutes, open book against the NEC 2026. Most other states, including Colorado, fold calculations into a single master exam instead.

Whatever the structure, if your state tests calculations, the questions come from a predictable set of subject areas — the same ones PSI weights on the Texas portion. If the knowledge questions reward code navigation, the calculation questions reward workflow: setting up the right load, finding the right table, applying the right correction and adjustment factors, and checking termination temperature limits. Here are the subjects any calculations portion draws from, and how to practice each one.

The subject areas behind the calculation questions

In Texas, per the TDLR/PSI Candidate Information Bulletin for the master examination, the scored calculation items distribute roughly as:

• Services and Service Equipment / Separately Derived Systems — the largest block, dominated by service and feeder load calculations and transformer-derived system sizing.
• Motors and Generators — a heavy second block: branch-circuit and feeder sizing for motors, motor overload and short-circuit protection, and generator applications.
• Branch Circuit Calculations — continuous-load 125% rules, receptacle and appliance loads, ranges and dryers.
• Feeders — demand factors, neutral loads, and voltage-drop considerations.
• Wiring Methods and Materials — conductor ampacity, derating for ambient and bundling, and raceway fill.
• Equipment and Devices, Control Devices and Disconnecting Means, Renewable Energy, and Special Occupancies — smaller but real presences.

Services and separately derived systems: where the points are

The single most tested calculation skill on the master exam is sizing service conductors for a commercial or industrial occupancy. That means the standard method of Article 220: general lighting and receptacle loads, continuous loads at 125%, demand factors for kitchens and laundry, and then the largest motor rule when feeders are involved.

Separately derived systems add a second layer: transformer primary and secondary protection (NEC 450.3), grounding electrode conductor sizing for the derived system (NEC 250.30 and Table 250.66), and the feeder tap rules when a transformer feeds a panelboard.

Motors: the second-highest weight

Motor calculations are where candidates lose the most time. You need to be fluent in the difference between:

• Branch-circuit conductors — sized at 125% of the motor full-load current (NEC 430.22), using the FLC from the tables in Article 430, not the nameplate.
• Overload protection — based on nameplate current, typically 115%–125% (NEC 430.32).
• Short-circuit and ground-fault protection — a separate device sized from the FLC table with the multiples in NEC 430.52.
• Feeder conductors — 125% of the largest motor plus the sum of the others.

Practice each of these as a distinct workflow — mixing them up is the #1 cause of wrong answers on motor questions.

Conductor sizing: corrections, adjustments, terminations

Ampacity questions on the master exam almost never end at Table 310.16. The full workflow is:

1. Compute the design load (continuous loads × 1.25).
2. Apply ambient temperature correction from Table 310.15(B)(2)(a) for the conductor insulation rating.
3. Apply the bundling adjustment for the number of current-carrying conductors in the raceway.
4. Size so the adjusted ampacity covers the load.
5. Check the 75°C termination column when the equipment is rated for 75°C terminations — which is the standard case.

If your state tests the NEC 2026, learn the renumbering

First confirm which NEC edition your state tests — your study plan and your tab placement depend on it. Texas and Colorado test the NEC 2026; Texas moved to the 2026 cycle on September 1, 2026, and its master examination follows it. The other seven states this platform serves test the NEC 2023. If you are testing on the 2026 edition, the structural changes you must know cold include the renumbered grounding and bonding articles, the new and renumbered articles for overcurrent protection and solar topics, and table moves that affect lookup questions. The exam is open book, so the skill is knowing where your edition puts the rule you need — muscle memory from an older edition will cost you minutes.

How to practice

The fastest way to build calculation fluency is timed, blueprint-weighted practice: for Texas candidates, a 33-item run at 170 minutes with the same subject mix PSI uses; for candidates in single-exam states, the calculation questions inside their state’s full-length simulation. Review every question with the exact article and table path shown. Master Electrician Practice builds each state’s simulations from that state’s official blueprint — the subject proportions come from the blueprint, not a random shuffle.

Start the first chapter free and work through the services and SDS calculations that anchor any calculations portion.